Method of heat-treating rolled steel sheets and plates.



G. A. WHITE.

METHODOF HEAT TREATING ROLLED STEEL SHEETS AND PLATES.

APPLICATION FILED JUNE 22, 1914.

Patented June 29, 1915.

To all whom itmay concern: a

GEORGE A. WHITE, or VANDERGRIFT, PENNSYLVANIA, ASSIGNOR T0 AMERICAN snnarr & Tm PLATE COMPANY, or PITTSBURGH, PENNSYLVANIA, A eonrotaA- TION OF NEW JERSEY.

Specification of Letters Patent.

Patented June 29, 1915.

Application filed June 22, 1914. Serial No. 846,580.

Be it known that I, GEORGE A. WHITE, a citizen of the United States, residing at Vandergrift, in the county of Westmoreland and State of Pennsylvania, have invented certain new and useful Improvements in Methods of Heat-Treating Rolled Steel Sheets and Plates, of which the following is a specification.

My invention relates to the manufacture of rolled steel sheets and plates, and while not restricted to such materials more particularly relates to sheets and plates rolled on a the hot mills of sheet and tin plate plants.

.Heretofore in the manufacture of sheets and plates, it has been the practice to anneal such materials by heating the materials either exposed to the direct heat of the furnace, which is termed open annealing, or in annealing boxes, which exclude the air from the sheets or plates during. the annealing operation and maintain the materials in a practically non-oxidizing atmosphere.

In open annealing sheets and plates a high elastic limit and high ultimate strength with low ductility are obtained. In box annealing sheets a low elastic limit and low ultimate strength with high ductility is the result obtained.

One object of my invention is to provide a method of heat treating rolled sheets and plates whereby the high ductility attained in box annealing is preserved without material reduction in the elastic limit and the tween the tensile strength and elastic limit of the materials.

Another object of my invention is to provide a novel method of annealing rolled sheets whereby the use of annealing boxes is overcome and avoided.

A further object of my invention is to provide a novel method of. annealing rolled sheets and plates in which the sheets or plates may be rapidly heat treated in an oxidizing atmosphere.

My invention consists in passing the sheets 7 and plates through a furnace in such manner that but a small part of the superficial area of the sheet or plate is in contact with the flame of the furnace at any one time.

The invention further consists in continucusly passing the sheets or plates from one end to the other through the heating zone of the furnace and subjecting successively constantly changing portions of the sheets and plates to the action of the heating zone of the furnace. a

The inventionstill further consists in permitting the successively heated portions of the materials to cool in the order in which they are heated.

Referring now to the drawing forming part of this specification, Figure 1 is a sectional side elevation showinga furnace constructed and arranged and adapted for use in carrying out my improved method. Fig.

2 is a sectional end elevation, the section being taken on the line II of Fig. 1, showing the arrangement of the feeding mechanism by which the plates are caused to travel through the heating furnace during the heat treatment of the sheets and plates. Fig. 3 is a diagrammatic, sectional end elevation showing an electric furnace constructed and arranged and adapted for use in carrying out my improved method.

In the drawings, referring to Figs. 1 and 2, the numerals 2 and 3 designate the side walls and 4: the end walls of the furnace,

- which isprovided with a combustion chamber 5 on each end, the furnace shown being s mmetrical about the line XX of Fig. 1. T e side wall 2 is provided with a lengthwise horizontal slot 6 forming a charging opening and the wall 3 with a similar slot 7 v forming a drawing opening, the plates and sheets A being passed successively through the slot 6 into the heating zone 8 of the furnace and then emerging through the slot 7. Rollers 39,-!) or shafts having a series of disks thereon to form the equivalent of the rollers 9 are located in front of the charging opening 6 to support the plates as they I are pushed into and through the furnace. A;

' the drawing.

The furnace is provided near each end with partition walls 11 and 12,.the lower end of the depending wall 11 terminating above the upper end of the wall 12 to form a port or passage for the entrance of the heated products of combustion into the heating chamberv 8 of the furnace. Oil or gas burners 13 of any approved type are employed on the ends of the furnace, air under pressure being employed with the gas or oil burners and being supplied thereto through the conduits or pipes 14, the supply being controlled by the valves 15. -The oil or gas is supplied by the pipes 16, which are connected to a fuel supply and the amount of oil or gas used is regulated by the valves 17 on the pipes 16.

In the apparatus shown in Fig. 3, the

heating chamber is formed by a hollow core 17 having openends and having side walls 18 and top and bottom walls 19 formed of a suitable refractory insulating material. The core 17 is wound with wire to form a core heating coil and the coil is surrounded by a covering 20 of brick or other refractory material. The coil 17 and covering 20 are mounted upon a suitable base or foundation 21. The end of the wire forming the coil 17 are connected by lead wires 22 and 23 with a transformer 24 and the transformer is nator, 27. A hand operated regulator 28 is connected in the circuit formed by the wires 25 and 26 and a volt meter 29 is connected in the circuit formed by the lead wires'22 and 23. Thealternator 27 is connected to a motor 30 by which it is driven. The furnace is provided with rollers 9 on the entrance side and ollers 10 on the discharge side of the heating chamber, in the same manner as in Figs. .1 and 2, to support the materials being treated, in passing the materials into and out of the furnaces. With the apparatus shown in Fig. 3 electric current, is passed through the coil 17 so as to heat the furnace chamber in the hollow core 18to the desired temperature.

In'carrying out my improved method the furnace is heated in any desired manner but preferably is heated by means of gas, air under pressure being supplied by a suitable blower. In this way the furnace is heated up to between 1800 and 2600 degrees F. the flame being highly oxidizing and the sheets and plates coming into direct contact with the oxidizing atmosphere of the furnace and being heated to a temperature of approximately 1600 to 2200 degrees F. in passing through the furnace.

The furnace, (Figspl we 2 being in heated condition in readiness for use, the plates or sheets A are successively fed into the charging opening 6 on the side 2 of the furnace'and then are caused to move continuously across the width of the furnace into and through the heating zone 8 and passing out through the discharge opemng 7 on the opposite side 3 of the furnace. The

furnace is made as narrow as possible in width or else is narrowed by other means so as to expose very narrowportions'ef the plate or sheet being heat treated to action of the flame in the furnace and the narrower the section of the plate which is exposed to the heating action, the better the result obtained. The plates are passed through the furnace of Fig. 3 in the same manner as has been described. The plates and sheets are caused to travel through the furnace at the rate of about 20 inches per minute, the

speed being varied with different thicknesses orv gages of sheets andplates, and as before stated, only a narrow section of the entire width of the plate or sheet is exposed tothe heating action of the heating zone of the furnace at any one time.

The results of the use of the method comprising my invention are that sheets and plates of improved physical characteristics are obtained and sheets and plates having a higher tensile strength and increased elastic limit and ductility are made possible.

Modifications in the construction of'the apparatus used in heat treating'the sheets or plates in accordance with my improved "'"method and changes in the steps of my improved method may be made without departing from my invention as defined in the claims. The sheets and plates may be annealed in a non-oxidizing atmosphere and other variations in the precise manner of heating the materials may be made within the scope of the appended claims.

1. The method of heat treating rolled steel sheets and plates which consists in""heating successively diflerentsections ofthe sheets to a temperature of approximately 1600 to 2200 degrees F.'and cooling the sections of the sheets or plates in the order in which they are heated.

2. The method f heat treating rolled steel sheets and plates which consists in heating successively different sections of the plate in an oxidizing flame and cooling the heated sections successively in the order in which they are heated.

3. The method of heat treating rolled steel sheets and plates which consists in heating successively different sections of the late in an oxidizing flame to a temperature tween 1600 and 2200 degrees F. and cooling the heated sections successively in the order in which they are heated.-

4. The method of annealing rolled steel sheets and plates consisting in heating nar- In testimony whereof, I have hereuntoset row sections of the sheets or plates, progresmy hand. sively changing the heated section of the GEORGE A. WHITE. sheet or plate and allowing the heated por- Witnesses:

5 tions thereof to 0001 in the order in which HtL. BODWELL, they are heated. R. G. Sco'r'r. 

